Antroduodenal manometry for the evaluation of patients with suspected gastroparesis

Background

This chapter will discuss the possible use and importance of antroduodenal manometry in the diagnosis and treatment of gastroparesis. As discussed in other chapters, gastroparesis is defined by symptoms of nausea, vomiting and abdominal pain. Generally there is a delay in the emptying of the stomach. There is a question as to whether these symptoms and signs are (1) due to an alteration in contractions of the stomach, pylorus, and duodenum or (2) incidental to the contractile pattern of these parts of the gastrointestinal tract. The presence of delayed gastric emptying with the presence of dyspepsia defines gastroparesis and differentiates the syndrome from chronic unexplained nausea and vomiting (CUNV) or gastroparesis-like syndrome .

The stomach and small intestine work as a coordinated unit to process and utilize ingested food by propelling the digested material out of the stomach and down the small intestine. Interest in the physiologic process controlling upper gut functional movement was stimulated by studies from dogs at the Mayo Clinic showing different motor patterns in the stomach and small intestine . The animal studies were expanded to humans using a water-perfused catheter to measure pressure changes in the small intestine . These studies suggested that aboral contractions through the stomach and small intestine contributed to normal flow of intraluminal contents and that these contractions differed during fasting from those in the postprandial period.

The alteration of the coordinated contractions of the stomach and the small bowel may contribute to symptoms of different clinical conditions such as gastroparesis, functional dyspepsia or intestinal pseudo-obstruction. Each of these conditions may or may not be associated with delayed gastric emptying. It is unclear if these different clinical syndromes are associated as part of a spectrum of disease.

Physiology of gastric emptying

There are several potential patterns that can be identified by recording motility from the stomach and small intestine. First is to determine the amplitude of intraluminal pressure resulting from contractions in each segment of the upper gastrointestinal tract. Second is to identify the pattern of contractions. The stomach, pylorus and upper small intestine work as a coordinated unit to grind food into small particles (<3 mm) and to propel the ingested food aborad into the intestine. This normal pattern allows digestion and absorption of the nutrients. In addition normally coordinated contractions prevent stasis of intestinal contents and potential reflux back into the stomach .

The stomach has multiple functions including accommodation to food, grinding of the food into small (2–3 mm) particles to allow passage through the pylorus, and coordinated contractions of the antrum, pylorus and duodenum to facilitate distal passage of the ingested food. A barostat measures tone of the fundus and analyzes gastric accommodation. This technique is discussed elsewhere. Antroduodenal manometry measures phasic contractions in the antrum, pylorus and duodenum. High-pressure or uncoordinated contractions in the duodenum can delay or decrease gastric emptying . Discrete ports of a manometry catheter best measure these abnormal phasic contractions of the small bowel. Pyloric contractions or tonal changes can be measured by a sleeve manometer or EndoFLIP .

Coordinated phasic contractions of the body and antrum of the stomach are initiated by interstitial cells of Cajal (ICC) concentrated in the pacemaker zone on proximal greater curvature. The ICC also are present throughout the stomach forming the conduction system. There are ICC which also pace intestinal motility, generating a plateau slow-wave frequency of approximately 11 cycles/min in the proximal intestine . There is a marked difference in the frequency of contractions between the stomach (3 cycles/min) and small intestine (11 cycles/min). In mice and rats ICC and slow waves are absent in the pylorus, although they appear present in humans . In healthy human controls, pyloric contractions are a mixture of antral-type and duodenal-type. Tonic and phasic pyloric contractions increase the resistance across the antroduodenal junction leading to gastric retention of ingesta .

In addition to measuring amplitude, frequency and coordination of antroduodenal contractions during fasting, the response to food is also important. During fasting a programmed motor pattern occurs . This interdigestive motor complex during fasting consists of a burst of continuous contraction followed by quiescent periods. This complex generally initiates in the stomach and migrates down the intestine approximately every 90 minutes. The migration out of the stomach moves larger indigestible materials (>3 mm in size) from the stomach and through the small bowel. This pattern functions as an “intestinal house keeper” sweeping sloughed cells and other debris toward the colon . Eating switches the pattern to a fed pattern consisting of an increased number of contractions with a less recognizable pattern.

Locally released neurotransmitters initiate different contractile patterns in the antrum and small bowel. In humans motilin stimulates a migrating complex only in the antrum and generally does not stimulate phasic contractions in the pylorus or duodenum . In the small intestine somatostatin agonists initiate the migrating complex .